For our client, Jan De Nul, underwater abrasive water jet cutting and general diving activities have been performed at South Riding Point in the Bahamas.

The abrasive water jet cutting technique has been used to cut an old water ballast pipe of 900m (2950ft) in manageable pieces. The pipe had the following sandwich structure:

• An internal sleeve of 762mm (30”)
• A steel pipe of 914mm (36”)
• Grout between the sleeve and the steel pipe
• A concrete coating of 100mm (4”)

Every 20m (787”), a window of 200x700mm (7.87” x 27.6”) had to be cut, while in the middle of the cut window, the sandwich structure was cut over the complete diameter from inside out.

Using the abrasive water jet cutting technique, a window was cut in approximately 45 minutes while a round cut was performed in approximately 1 hour.

The main advantages of the abrasive water jet cutting technique are that:

• It can be performed diverless
• It can be applied in the presence of oil or gas since there is no open fire
• Environmental friendly due to the use of natural sand and water as cutting consumables
• Any desired shape can be cut: round, square, from inside to outside, from outside to inside, …
• All kind of materials can be cut, even combinations of materials

All abrasive water jet cutting tools are custom build, designed and tested in-house and the project was thoroughly evaluated resulting in a custom made solution.

The cutting and the diving activities in the Bahamas were very successful. The good cutting result can clearly be seen in the pictures.